This invention relates in general to internal combustion engine and electric powered hybrid vehicles. In particular, this invention relates to an improved electrical system for hybrid vehicles.
Hybrid electric vehicles, generally, are vehicles that use electricity, to at least some degree, to supply motive power or limit the use of conventional internal combustion (IC) power sources. Hybrid vehicles are often defined by their powertrain layout and the degree to which electric motors influence power consumption. Two broad categories of hybrid vehicle powertrains, having both IC engines and electric propulsion, are parallel hybrids and series hybrids. Parallel hybrids, generally, have a powertrain layout where an IC power source and an electric power source combine to provide power to the wheels. Alternatively, some parallel hybrids connect the IC source and the electric power source to a common point, such as a transmission, and transmit power to the wheels from that point. Series hybrids, generally, use electric motors to drive the wheels and an IC engine drives a generator to augment/charge the batteries or power the motors directly.
Hybrid electric vehicles may also be categorized by the degree of hybridization, that is the amount of propulsion available from an electrically powered source. Full hybrids, which may be series or parallel powertrain arrangements, typically can drive the wheels by the IC engine, batteries powering electric motors, or a combination of both. Mild hybrids, on the other hand, rely on the IC engine for the main source of motive power and utilize electric power to improve efficiency. Some mild hybrids improve IC engine efficiencies by limiting the conditions that call for engine power. For example, IC engines having starter/alternator systems will shut the engine off during idling conditions and run accessories through an accessory drive electric motor. The starter/alternator will restart the engine when the driving cycle is initiated or when a secondary electric motor driving capacity is exceeded. Other mild hybrids augment IC engine output by using a motor/generator on the non-driving wheels to capture braking energy to recharge batteries. These motors may also provide limited driving power prior to the IC engine demand.
Many hybrid architectures, particularly full hybrids and mild hybrids, rely on a low voltage battery source, for example a conventional 12 volt battery, to start the IC engine and a high voltage battery source, for example a 48 volt to a 300-plus volt source, to store energy and power wheel motors. Because vehicle weight directly impacts efficiency and cost, there is a need to improve hybrid vehicles to fully utilize available power sources. In addition, packaging space in hybrid vehicles is particularly limited due to the size of batteries. Thus, it would be advantages to provide an electrical system, particularly for a hybrid vehicle, that reduces the number of battery systems need to power a vehicle.